1. Field of the Invention
The present invention relates to induction heaters, more specifically to an induction heater and an induction heating method for heating by induction a work in which a gear portion and a shaft are integrated.
Simultaneously, the present invention relates to an induction heater and an induction heating method for heating by induction a work having a gear portion and a stepped shaft.
2. Description of the Related Art
Conventional induction heaters employ various forms of heating coils corresponding to shapes of objects to be heated by induction. A patent document 1 specified below proposes a heating coil having a form applicable to heat by induction a shaft having different diameters. Specifically, a connecting part between a small-diameter part and a large-diameter part is difficult to be appropriately heated (hardened) by induction although being readily subjected to stress. However, the induction heater as disclosed in the patent document 1 efficiently hardens the connecting part.    Patent Document 1: JP 2000-87135 A